With particular reference to physiological control systems in mammals and more particularly those of the human body it has been noted that the control systems which the body itself uses to control various organs are complex.
For example, the heart of a mammal may cause the amount of blood that is to be circulated through the body to change not just for what might be termed obvious reasons such as an increase in physical exertion by a person, but may also occur for example, as a result of anticipation of exertion. Furthermore the triggers which can cause changes in heart rate and pumped blood volume may derive from the nervous system directly or may derive from the action of hormones or other chemical releases within the body.
It follows, where mechanical aids are introduced into the body to assist the body's functions such as, for example, implantable rotary blood pumps used as ventricular assist devices that simplistic control mechanisms for these mechanical aids cannot hope to anticipate or mimic the commands which the body may pass to the heart.
For example, in early applications of ventricular assist devices the control mechanisms simply set the ventricular assist device to pump at a constant volume per unit time, adjusted at the time of initial installation to best suit the patient in whom the device has been installed.
Such systems use pump speed as the controlled variable. Unfortunately, a set pump speed bears no relation to actual physiological demand.
It is an object of the present invention to address or ameliorate one or more of the above mentioned disadvantages.